Small angle neutron scattering studies of hard magnetic bulk amorphous alloys

Bulk cylinders of Nd 60 Fe 30 − x Co x Al 10 obtained by slow cooling from the melt have been studied by SANS using polarized neutrons. Two Curie temperature have been found at T c 1 = 50  K and T c 2 = 500  K revealing the presence of two magnetic phases. The sample exhibits a partially crystalline structure which leads to large coercivity of the alloy. Measurements have been performed at temperatures between 2 and 550 K with an applied magnetic field up to 6 T. Nanosized Nd-nanoparticles in the Fe-rich part of the alloy have been identified acting as pinning centres, which prevent the full alignment of ferromagnetic domains even in high magnetic field.